Photographic composition containing epoxy hardening agents



emulsion or other unwanted characteristics.

United States Patent This application is a continuation-in-part of application Serial No. 810,571, filed May 4, 1959, now U.S. Patent- 3,09l,537. This invention relates to the hardening of photographi emulsion layers or of gelatin or other polymeric-material used for colloidal layers in photographic products which comprises incorporating quaternary ammonium compounds which contain at least two epoxide groups, in

compositions thereof.

Various agents have been'employed for hardening gelatin or other polymers such as are employed for photographic layers or as carriers for silver halide-photographic emulsions. Some ofthese which might be mentioned are formaldehyde, chrome salts, dialdehydes, hydroxy aldehydes and the like. Often one or the other of the com pounds which have been previously suggested for hardening-purposes for photographic products exhibit disadvantages such as etfect on the sensitivity of the photographic Many of the hardeners suggested have been volatile, fat-soluble, or unstable in aqueous solution or have not been photographically inert.

One object of my invention is to provide for the hardening of gelatin or other polymeric materials used in photographic layers by incorporating quaternary ammonium compounds, containing at least two epoxide groups therein, in compositions of the polymeric materials. Another object of my invention is to provide gelatin or other polymeric products having carboxyl and/or amino groups therein with hardening agents which are. non-volatile, stable in aqueous solution and non-fat soluble. Other objects of my invention will appear herein.

1 have found that quaternary ammonium compounds containing at least two epoxide groups therein exhibit satisfactory hardening properties when used in gelatin compositions employed either as carriers for silver halidephotographic emulsions or for applying layers in the manufacture of photographic products. I have found in addition that these compounds exert a hardening effect upon carboxyl-bearing polymers useful for the purposes speci- The quaternary ammonium salts containing at least two epoxide groups therein are used as hardeners in an amount at least-%% based on the weight of the gelatin or other polymeric material. In practice, not more than percent is needed, based on gelatin weight. The proportions, however, of the hardeners in accordance with my invention are not critical, in that proportions less than have been found to exhibit a hardening effect on gelatin or carboxylbearing polymers and on the other hand proportions thereof greater than 10 percent will result in a hardening effect when incorporated in compositions of gelatin or other carboxyl containing polymers.

The-anion of the quaternary ammonium salts may be BEST AVAILABLE COPY ICC that of any convenient'acid, although because of casein 7 their preparation, the perchlorate and sulfonate salts have been preferred. However, the chloride, sulfate, phosphate or the like may be employed for hardening purposes to good effect.

The quaternary ammonium salts useful for hardening may be entirely aliphatic or they may contain cyclo aliphatic groups or aromatic groups therein. -In some cases, cyclic compounds containing nitrogen in the ring may be used to supply the nitrogen for-the quaternary ammonium structure ofthe hardener.

Compounds useful as hardeners in accordance with my invention are relatively easily prepared in good yield and may be a variety of types. The following equations exemplify procedures by which compounds useful for hardening purposes are prepared.

lon- 1 I I case on 0.1m: -(cn,o --on, 1 'cmmtcmc ono,

CyHrSOr V (In (I) It is apparent from Equation 1 that the amine may consist of any of the lower aliphatic or aromatic primary amines and the alkylating agent may be selected from the alkyl sulfonates, sulfates, halides, or the like. In Equation 2 instead of a lower aliphatic secondary amine certain heterocyclic amines, such as piperidine or morpholine may BEST AVAILABLE'C'OPY housed. .ln Equation 3 the bisull'onatc might contain unsaturation; hetero atoms or ringr; or the corresponding dihalide might be used. Other di-stcondary amines can be employed in place of the piperazine in Equation 4. Sometimes in the preparation of the quaternary ammonium compounds, difficulty is experienced in obtaining crystalline salts. It has been found, however, that an entirely satisfactory hardener may result when the reaction product is isolated as a concentrated aqueous solution and'used in that form.

- The polymeric compounds which may be hardened by quaternary ammonium compounds containing bisepoxide groups in accordance with the invention are those containing amino and/or carboxyl'groups. Many of these polymers havebeen used for supplying coatings in the manufacture of photographic products or as carriers for silver halides in' photographic emulsions, such as gelatin, celluloseether phthalate and synthetic resins. Gelatin and carboxyl containing polymers are readily hardenable by incorporating quaternary ammonium compounds therein in accordance with our invention. The cellulose ethyl ethers containing carboxyl groups as have been described in U.S. Patent No. 2,725,293 as being useful as carriers for silver halide are hardenable by means of quaternary ammonium compounds in accordance with my invention. Examples of polymers containing carboxyl groups hardenable by quaternary ammonium compounds as described herein are ammonium salts of poly(butyl-acrylate coacrylic acid), sodium salts of phthalated polyvinyl alcohohammonium salts of phthalated gelatin, ammonium salts of phthalated polyvinyl alcohol, ammonium salts of copolymers of acrylic acid (30-40 mol percent) and one or more of the following esters; butyl methacrylate,

butyl acrylate, ethyl acrylate, ammonium salts of poly (buty'lacrylate-acrylo nitrile-a'crylic acid), etc.

we have found that when hardeners as described herein are incorporated in compositions of these polymers and the compositions are coated out onto a surface and the coating is dried, such as by warm dry air, hardening of the polymeric material takes place in a short time as evidenced by improved resistance to the efiect of hot water and by an appreciable increase in the melting point ofthe coating as compared with the same polymeric material in which no hardener has been incorporated. The polymeric layer is hardened by the quaternary ammonium compound upon standing or aging such as for two or three days at normal temperature. With curing at an elevated temperature hardening results in a shorter time.

The following examples exemplify methods of preparing quaternary ammonium compounds'and illustrate the use of those compounds as gelatin hardeners in accordance with my invention.

' EXAMPLE I 295 parts of epichlorohydrin was added dropwise to a mixture of 295 parts of n-propylamine and 4.5 parts of water. The temperature was maintained at 25-28 during this addition and for 6 hours thereafter. A solution of 142 parts of sodium hydroxide in 230 parts of water was then added dropwise to the mass while cooling below 25 C. After 1 /2 hours the top layer was separated, combined with ether extracts of the aqueous layer and the whole was dried over potassium hydroxide pellets for several days. The product obtained was filtered and distilled yielding 134 parts of product, boiling at 102.5 C. This product was N,N,bis(2,3-epoxypropyl)propylamine.

- 17.3 parts of the amine so prepared was mixed with 18.6 parts of methyl paratoluene sulfonate in 20 parts of benzene and the mass was allowed to stand at 25' C. for 16 hours. The lower oily layer was separated, washed with benzene and was dissolved in 45 parts of water. This solution was washed with three separate portions of henzone and was subjected briefly to reduced pressure to remove traces of the benzene. The resulting solution con- 4 tained about 42 percent by weight of bis-.(2,3-epoxypropyl) methylpropyl ammonium p-toluenc sulfonate:

A solution of 27.8 parts of 3-diethylamino-l,2-epoxy- H propane (prepared according to Gilman and Fullhart, JACS 71, 1478) in 25 parts of benzene was mixed with a neutral solution of 26 parts of LS-dimethane sulfonoxy pentane in 25 parts of benzene. The mixture was allowed to stand 16 hours whereupon the mixture was heated on a steam bath for 6 hours. It was then cooled and the lower layer was separated and dissolved in-75 parts of water. After separating from the undissolved fraction the aqueous solution was treated with charcoal, washed with benzene and was treated briefly at reduced pressure to remove traces of benzene. The-solution ob tained contained approximately 30 percent of 1,5-pentane bis(2,3-epoxypropyl diethyl ammonium methane sulfonate).

EXAMPLE III A suspension of 12 parts of 1,4-dimethanesulfonoxy-2- butyne in 50 parts of benzene was mixed with 11 parts of S-dimethylamino-1,2-epoxypropane. The mass was stirred for one hour on a steam bath, following which it was cooled and the lower layer was dissolved in 25 parts of water and washed with benzene. This solution was treated with charcoal and then with a concentrated aqueous solution of sodium perchlorate. The oil which separated gradually crystallized at 0 C. These crystals, brown in color, were extracted with acetone and ethanol. After several recrystallizations from acetonitrile-ethyl acetate, cream-colored granular crystals of 2-butyne-1,4- bis(2,3-epoxypropyldimethyl ammonium perchlorate) were obtained.

The quaternary ammonium salts prepared in accordance with the above examples were incorporated in aqueous gelatin compositions which were coated out onto support in the form of a layer thereon. The melting properties of these layers were compared with those of The designations 212-1 and 212-2 indicate that it was necessary to hold the temperature at boiling for one or two minutes, respectively, before any melting of the gelatin layer was observed.

EXAMPLE IV 222 parts of epichlorohydrin at 25 C; was added dropwise to 121 parts of a 40 percent solution of methylamine in water. Cooling was necessary to hold the temperature at 20-30 during the addition and for three hours thereafter. 208 parts of a solution of 50 percent sodium hydroxide was then added at a temperature of less than 25 C. and the mass was stirred for 1% hours. The top layer which formed was separated and was combined with ether extracts of the bottom aqueous layer and the mass was dried over potassium hydroxide pellets for several days. The mass was filtered and distilled at reduced pressure (20 mm.) at 104-107 C.

7.1 parts of the N,N-bis(2,3-epoxypropy1)methylamine 2.0% blst2,8epoxypropyl)cthyl methyl BEST AVAILABLE COPY formed thereby was mixed with 9.3 parts of methyl para toluene sulfonatc and 15 parts of benzene and the materials were allowed-to react for .5 hours whereupon the benzene was decanted oil. The syrupy residue which resulted was dissolved in 80 parts of acetone and a solution of 13 /2, parts of sodium perchlorate in 13.5 parts of acetone was added. The mixture was filtered, the acetone was evaporated offand the residue was dissolved in water. The solution was washed with benzene and treated with activated carbon. There was obtained 37 parts of a pale yellow solution containing 32pcrcent of bis(2,3-epoxypropyl)dimethyl ammonium perchlorate.

EXAMPLE V A solution of 102 parts of piperazine in 100 parts of The mixture was 'cooled, filtered, and the mixture was washed with ligroin. The product was recrystallized from 1200 parts of ethyl acetate giving 106 parts of colorless 'bischlorohydrin (M.P. 1015-103); The filtrate was cooled to 60 C. producing 16 parts of isomeric bischlorohydrin, having a melting point of 82-84 C.

45 grams of the higher melting bischlorohydrinobtained as described was mixed with a solution of 120 parts of sodium hydroxide in 200 parts of water at 50 C. The mass was stirred for 56 hour at that temperature and was extracted with benzene. This extraction was repeated A 'hour later and the two combined filtered extracts were evaporated to dryness. The crude product obtained, l,4 bis(2,3-epoxypropyl)piperazine dihydrate, was recrystallized from ether. A mixture of 7 parts of this product and parts of methyl p-toluene sulfonate in 15 parts of methanol fwere refluxed for one hour. The solvent was slowly evaporated from the'mass at room temperature and 1.8 parts of crystals were obtained which after recrystallization from ethanol melted at 240-2415 C. The

bulk of the crystalline product melted at 205-215 C. after crystallization from ethanol. The product obtained'was a quaternary ammonium salt designated as 1,4-bis(2,3- cpoxypropyl)-1,4-dimethyl piperazinium di-p-toluene sulfonate.

EXAMPLE VT N,N-bis(2,3-epoxypropyl)ethylamine was obtained by the procedure described in the first part of Example I except that ethylamine was employed instead of propylamine. This material was reacted with methyl paratoluene sultonate in the manner similar to that described in Example I. There was obtained a 48 percent solution of quaternary salt designated bis(2,3-epoxypropyl)ethyl-methyl ammonium paratoluene sulfonate.

The following table illustrates the hardening effects .of these quaternary ammonium bisepoxides on photographic emulsions.

Hardcner (on wt. of gelatin in emulsion) Age at 607 2.0% bls(2.3-epoxy ropyl)mcthyl propyl ammonium p-to ucnesulfonate.

2.0% bis(2,3-epoxypropyl)dlmethyl ammonlurn perchlorate.

ammounlum p-tolucnesullonate.

2% 2-butyne l, l-bls(2,$epoxypropyl dlethyl ammonium perchlorate).

The following table illustrates the hardening effect of various bisepoxides in gelatin solutions employed for photographic purposes.

Table II.-Hardening of gelatin by the above bisepoxides Age at 50% Hardenerton wt. of gelatin) R.H., 77 F.

2.0% l tis(2,3-cpolypropyl) methyl propyl ammonium p-tolucne-sullonste.

2.0% i.ls(2,3-epoxypropyl)dlmethyl ammonium perchlorate.

2.0% bis(2,3 epoxypropyi) ethyl methyl ammonium p-tolucne-sulloneto.

2.0% Z-butyne l 4-bls-(2,3- epoxypropyl dlmethyl ammonium perchlorate).

EXAMPLE VII 5 parts of a 48 percent solution of the quaternary ammonium salt prepared in Example VI was mixed with a solution of 2 parts of sodium tetraphenyl boride in 15 parts of water. The percipitate which formed gradually crystallized when the mass was cooled by an ice bath.

The product was purified by recrystallizing from acetone.

It was found to melt at 209-211 C. This material was effective as a hardener in aqueous gelatin coating compositions.

EXAMPLE VIII 40 parts of N,N-bis(3-chloro-2-hydroxypropyl(panisidine was suspended in 500 parts of dry ethyl ether and there was added thereto with stirring under reflux 40 parts of powdered potassium hydroxide. The mixture was filtered, the filtrate was shaken with activated alumina and it was then filtered and distilled giving 26 parts of N,N-bis- (2,3-epoxypropyl) -p-anisidine. 5 parts of this product was heated with 4 parts of methyl p-toluene sulfonate on a steam bath for 2 hours. Treatment with benzene gave crystals which were re-crystallized from 2-butanone. This product was N,N-bis(2,3-epoxypropyl)-p-anisidine methop-toluene-sullonate.

Portions of high speed bromoiodide photographic emulsion optically sensitized with a cyanine dye without addition and with additions of 1.2% and 6.1% of N,N- bis(2,3-epoxypropyl)-p-anisidine metho-p-toluene sulfonate respectively were coated out upon a suitable cellulose acetate film base. The films so obtained were exposed in an Eastman 1B Sensitometer and developed in Kodak Developer DK-SO for 5 minutes. The film was then fixed, washed and dried. The results obtained were set out in the following table. The relative speed values used in the table were inversely proportional to the exposure re quired to produce a density of 0.3 above fog. The melting points are of the coatings before processing. The value 212 F., 2 minutes, indicates that no melting was observed when the strips were subjected to this temperature for two minutes. r

. gelatin and was found to measurably decrease the percent swelling of coatings thereof by aqueous liquids.

Fresh tests 1 week 120 1niercent on eubatlon Retieule- Melting Hnrdenor weight of tton point Speed 1 Fog Speed 7 Fog control 100 1.37 .14 as 1. 06 .17 so? 86F. N,N-his(2.3-eporypropyD- 1.2 102 1.20 .11 60 .TI .16 Noue 134 F., p-anisldtnnmetho-pstripped.

toluene sultonate.

6.1 102 1.17 [.11 Noue 212 F..

' 2min.

EXAMPLE 1X EXAMPLE XI.--P XYLYLENEBIS[N,N BlS(2,3-

A silver halide photographic emulsion of the type described in Henn and Gotie US. application Serial No. 746,078 containing as the carrier for the silver halide 86 grams of ethyl acrylate-acrylic acid copolymer and 37 grams of gelatin per mole of silver was prepared. Various concentrations of bis-2,3-epoxy-propylethy1-methyl ammonium p.-toluene sulfonate were added to samples of the emulsion and' the samples were coated onto a cellulose acetate film .base with the following results.

Mushiness (tn grams; at

room temp.) Reticulu- Conc. ln gms/Ag mole tion in water, F

Dev. Fir Wash .4 13 Stripped 80 74 92 78 none 98 118 93 none 106 130 108 none Mushiness is an internal physical measurement test and concerns the placement of a pointer directly over the emulsion side of a film sample. The pointer touches the emulsion surface, thesample being present in either developer, fixer or water, with no weight attached to it. Subscquently increasing gram weights are added to the top of the pointer so that increasing pressures are'cxerted on the emulsion. The number of grams on the pointer at the time the emulsion first ruptures indicates its resistance to pressure. High mushiness values are advantageous; .low mushiness values are disadvantageous.

The following three examples relate to the preparation of compounds. containing a plurality of epoxy groups which are useful as hardeners for gelatin and for carboxyl containing polymers.

EXAMPLE X.-2 BUTYNYLENEBLS[N,N BIS(2,3- EPOXYPROPYL)-N'-METHYL AMMONIUM MES- YLATE] 8.5 grams of 1 ,4-bis(methanesulfonqxy)-2-butync and 10.7 grams of N,N-bis(2,3-epoxypropyl)methylamine were dissolved in 25 ml. of acetonitrile and the solution was stirred at 25-33" C. for 17 hours. Ether was added whereupon a gum precipitated. This gum was washed several times with warin ether and was then dissolved in .250 ml. of acetonitrile. The solution was dried over magnesium sulfate and decolorized with charcoal whereupon the solute was reprecipitated with cold ether and most of; the residual solvent was removed in vacuo to give l7 grams of the above mentioned material as a colorless, hygroscopic, plastic mass. This material was added to silver halide photographic emulsion in various concentrations such as 1, 3 and 6 grams per 100 grams of CHLORATE] on. on.

A mixture of 9.3 grams of p-xylylene dibromide and and 10.8 grams of N,N-bis(2,3-epoxypropyl)methylamine in ml. of acetonitrile was heated gradually to 50 C. and held at this temperature for 2 hours. The mixture was cooled, the solvent was decanted and the residue was washed with warm acetonitrile. The residue was then dissolved in 20 ml. of water, washed with benzene and the aqueous solution was treated with a concentrated aqueous solution containing 10 grams of sodium perchlorate. A gum precipitate was obtained. This precipitate was crystallized from dilute ethanol to give 11.1 grams of crude product. It was then recrystallized from dilute ethanol and acetonitrile-ethyl acetate to give colorless, granules of the compound mentioned above. This compound was incorporated in silver halide photographic emulsion samples in various proportions and when those samples were coated onto a support was found to measurably increase their resistanoe to swelling in water as compared with like samples but without hardener.

EXAMPLE XII.POLY[2 BUTYNYLENE N,N

BIS(2,3-EPOXYPROPYL) PIPERAZINIUM DIMES- YLATE] chr stian, cmofiouslazomsor it it EC CH1 CHgCE 12 grams of 1,4-bis(methanesulfonoxy)-2-butyne and 9.8 grams of 1,4-bis(2,3-epoxypropyl)piperazine was dissolved in 55' ml. of acetonitrile and the solution was stirred for 14 hours at 2530 C. and then refluxed for vacuo. The product was that designated in the heading of this example. This compound was added in varied concentrations to samples of a high speed silver-halide gelatin photographic emulsion and the emulsion samples were coated onto support.

In each of the above three examples the coatings contained 1040 mg. of gelatin per square foot, each emulsion sample being coated on a cellulose acetate film support at a silver coverage of 459 mg. per square foot. A sample of each film coating was exposed on an Eastman lB Sensitometer, processed for 5 minutes in Kodak DK-SO developer, fixed, washed and dried. It was found that the emulsion coatings showed a substantial increase in resistance to swelling by water as compared with emulsion coatings not containing hardener.

Samples of the compounds prepared in Examples 10, 11 and 12 were added to separate portions of a high-speed silver bromo-iodide emulsion which had been panchromatically sensitized with a cyanine dye. Each emulsion sample was coated on a cellulose acetate film support at a silver coverage of 459 mg. per square foot. A sample of each film coating was exposed on an Eastman 1B Sensitometer, processed for 5 minutes in Kodak DK-SO developer, fixed, washed and dried with the following resultsf Each of the above coatings contained 1040 mg. of

' gelatin per square foot.

The ammonium salts are most conveniently added to gelatin solutions in the form of aqueous solutions. However, if desired, some other solvent may be employed in admixture with water. If the solution of quaternary is to be stored for a long period of time it is ordinarily preferable to dissolve in some other solvent than water. For

coating compositions having a pH within the range of 5-9 the effective aging time is substantially uniform.

With a pH outside of this range longer aging times are ordinarily required to obtain the desired degree of resistance to the reaction of hot water. The advantage of hardening in accordance with our invention is that water insolublecoatin'gs are obtained under conditions which are very mild; hence, the coatings can be hardened or insoluhiliz ed without any adverse effect on sensitive sub stances which might be present in the composition to be hardened.

The polyepoxide salts are useful not only as hardeners for gelatin but also for hardening carboxyl-containing polymers. One polymer of this type is the water soluble salt of a carboxy cster-lactone of an interpolymer of an unsaturated alpha-beta-dicarboxylic acid and a vinyl ester of a carboxylic acid which is ordinarily used in the form of its water soluble salt. A solution was prepared in water of 5% of this carboxyl-containing polymer, 0.15% bis(2,3-epoxypropyl) dimethylammoniurn p-tosylate and 0.05% p-tert.-octylphen0xy diethoxyethyl sodium sulfonate. The pH of the solution was adjusted to 7. This solution was coated onto a' gelatin subbed cellulose triacetate film base and was dried by blowing hot air over the surface ofthe coating. Another coating was prepared in identical manner except that the epoxy compound was omitted. Strips of both coatings were aged for seven days at 77 F. and 50% and thewet adhesion of these coatings on the film base was determined by immersing the coatings in dilute alkali and distilled water. The coating which contained the epoxy compound was insoluble in both solutions. The coating without the epoxy compound dissolved off of the support instantaneously.

In another test the vertical swell of the two coatings was measured in a mildly alkaline developer after different periods of incubation at 77 F, and RE. The epoxy containing coating after one day's incubation had a vertical swell of 750%; that after seven days incubation and that after days incubation both had a vertical swell of 300%. The coating without the epoxy compound therein dissolvcd in the developer.

Other coating compositions were prepared using aqueous solutions of the water soluble salt of a carboxy esterlactone of an interpolymer of an unsaturated alpha-betadicarboxylic acid and a vinyl ester of a carboxylic acid and each of the following cross-linking agents were added to separate portions respectively:

(I) Poly [2 -butynylene-N,N'-bis(2,3-epoxypropyl)- pipcrazinium dimesylate] (2) 2 Butynylenebis[N,N bis(2,3 epoxypropyl)-N- methyl-ammonium mesylate] (3) p Xylylene bis[N,N bis,2,3-epoxypropyl) N methyl-ammonium perchlorate] The solutions and coatings on cellulose triacetate gelatin-subbed film support were prepared in the same manner .as in the previous example. The coated films were subjected to an incubation period and were then tested for vertical swell. It was found that the coatings thus supplied were greatly improved in vertical swell over coatings of the carboxyl containing polymers having had no addition of the polyepoxy compound thereto.

I claim:

1. A photographic element comprising a layer which contains cellulose ether phthalate having a phthalyl content of at least 20% by weight and as a hardener therefor, a quaternary ammonium salt containing at least two oxirane rings separated from the quaternary nitrogen by a single carbon atom.

2. A composition of matter comprising a water-soluble salt of a carboxy ester-lactonc of an interpolymer of an unsaturated alpha-beta dicarboxylic acid and a vinyl ester of a carboxylic acid and a hardening amount of p-xylylene bis[N,N-bis-(2,3-epoxypropyl)-N-methyl-ammonium perchlorate].

3.. A composition of matter comprising a water-soluble salt of a carboxy ester-lactone of'an interpolymer of an unsaturated alpha-beta dicarboxylic acid and a vinyl ester of a carboxylic acid and a hardening amount of bis(2,3- epoxypropyl) dimethyl ammonium p-toluene sulfonate.

4. A composition useful forapplying layers in the preparation of photographic products which comprise a 5%' solution in water of a water-soluble salt of a carboxy esterlactone of an interpolymer of an unsaturated alphabeta-dicarboxylic acid and a vinyl ester of a carboxylic acid which solution contains 0.15% of bis(2,3-epoxypropyl) dimcthylammonium 'p-tosylate and 0.05% p-tert.-octylphcnoxy diethoxyethyl sodium sulfonate.

References Cited by the Examiner UNITED STATES PATENTS 7 2,725,293 11/55 Talbot et a1. 96-l I 3 2,861,056 11/58 Minsk. 3,091,537 5/63 Burness 96-111 NORMAN G. TORCHIN, Primary Examiner. 

1. A PHOTOGRAPHIC ELEMENT COMPRISING A LAYER WHICH CONTAINS CELLULOSE ETHER PHTHALATE HAVING A PHTHALYL CONTENT OF AT LEAST 20% BY WEIGHT AND AS A HARDENER THEREFOR, A QUATERNARY AMMONIUM SALT CONTAINING AT LEAST TWO OXIRANE RINGS SEPARATED FROM THE QUATERNARY NITROGEN BY A SINGLE CARBON ATOM. 